1. Technical Field
This invention generally relates to object oriented programming and more specifically relates to a mechanism and method for creating one or more class archive files from one or more existing class archive files.
2. Background Art
The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely sophisticated devices, and computer systems may be found in many different settings. Computer systems typically include a combination of hardware (e.g., semiconductors, circuit boards, etc.) and software (e.g., computer programs). As advances in semiconductor processing and computer architecture push the performance of the computer hardware higher, more sophisticated computer software has evolved to take advantage of the higher performance of the hardware, resulting in computer systems today that are much more powerful than just a few years ago.
Computer systems typically include operating system software that controls the basic function of the computer, and one or more software application programs that run under the control of the operating system to perform desired tasks. For example, a typical IBM Personal Computer may run the OS/2 operating system, and under the control of the OS/2 operating system, a user may execute an application program, such as a word processor. As the capabilities of computer systems have increased, the application software programs designed for high performance computer systems have become extremely powerful. Additionally, software development costs have continued to rise because more powerful and complex programs take more time, and hence more money, to produce.
One way in which the performance of application software programs has been improved while the associated development costs have been reduced is by using object-oriented programming concepts. The goal of using object-oriented programming is to create small, reusable sections of program code known as xe2x80x9cobjectsxe2x80x9d that can be quickly and easily combined and re-used to create new programs. This is similar to the idea of using the same set of building blocks again and again to create many different structures. The modular and re-usable aspects of objects will typically speed development of new programs, thereby reducing the costs associated with the development cycle. In addition, by creating and re-using a comprehensive set of well-tested objects, a more stable, uniform, and consistent approach to developing new computer programs can be achieved.
A central concept in object-oriented programming is the xe2x80x9cclass.xe2x80x9d A class is a template that defines a type of object. A class outlines or describes the characteristics or makeup of objects that belong to that class. By defining a class, objects can be created that belong to the class without having to rewrite the entire definition for each new object as it is created. This feature of object-oriented programming promotes the reusability of existing object definitions and promotes more efficient use of program code.
Many object oriented programming languages allow packaging multiple classes together in a class archive file. Because an archive file can contain many different classes, a software application that needs to access many of these classes can access all the classes it needs from a single archive file. The use of archive files is especially useful in an Internet environment, where download speed is often a bottleneck to performance.
If a software application (or a downloadable software application known as an applet) requires multiple classes, and if these classes are each individually available for download, the web browser would have to open a connection, download a class, and close the connection for each class that needs to be downloaded. Thus, if sixty classes are required, the web browser must repeat sixty times the sequence of opening a connection, downloading one class, and closing a connection. If the same sixty classes are packaged into an archive file, the web browser only has to make one connection, download the archive file (which contains all sixty classes), and close the connection. Thus, by using an archive file, the web browser has saved the time it would have taken to open and close fifty nine connections.
The current trend in object oriented programming has seen a dramatic increase in the size of class archive files. The more classes that are packaged into a single archive file, the more applications and applets will be able to run using the archive file. However, the growth of the size of archive files, while convenient for software vendors, increases the download time of an application or applet that uses classes contained within the archive file, and increases the space required to store the archive files on disk. Some archive files have become so large that the download time has become excessive, especially considering that only a small percentage of classes in a large archive file is used by any particular application or applet. Thus, the benefit of packaging multiple classes together in an archive file is now being offset by longer download times caused by the tendency to include a relatively large number of classes to support a large number of different applications and applets. Without a mechanism for generating smaller archive files from one or more existing archive files, the computer industry will continue to suffer from archive files that are excessive in size and therefore create delays in loading the archive file for use.
According to the preferred embodiments, a tool referred to herein as an archive maker operates on one or more existing archive files that contain multiple object oriented classes to generate one or more new archive files. The archive maker takes a list of required classes, analyzes those classes in one or more existing archive files to determine any classes upon which they depend, and creates a new archive file with all the required and dependent classes. This allows the classes that are not required for a particular application or applet to be stripped out of the archive file. The archive maker may also be used to partition an existing archive file into multiple new archive files according to one or more partition criteria. In addition, the archive maker may be used to consolidate multiple existing archive files into a single new archive file.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.